I wrote this here as well, but I thought I should make a seperate post so we could talk about it in depth.  I'd really like to see testers talking about this one, because I think it could make a big difference in gameplay -

This might be a five-pointer, but I think it would be worth it.  Actually if devs made one major change before release this should be it, imo..

Currently control spells like stun and snare are coded to replace spells of the same type that are already in effect.  So TB warps in and Frost Novas Regulus - Regulus is frozen - Rook walks up and Boulders Reg while he is frozen - Reg is now stunned - Hammer and Shatter come down GG. 

Instead spells should be coded to disallow replacement.  If Rook Boulders while Regulus is still frozen by FNova then the boulder gives damage but no stun effect.  The spell is wasted, and Regulus has a chance to fight or run when Nova expires, as opposed to simply dying, every time. 

Or take Wyrmskin Gloves.  If your attack speed is high enough you can keep a target in perpetual slow, because the duration is long enough and chance to proc high enough that the slow will be replaced indefinitely.  Through some Snare or Diseased Claws in there, maybe a Mine or QoT's insanely longrange slow, and you can keep the target from going anywhere until they die.  In the new model only one slow at a time can be effective.  It still makes a difference, but it doesn't cause the ragequits I'm seeing under the current model, I don't think. 

Without replacement effects all those secondary spells would be wasted unless you trigger them after the first one expires so you introduce a whole new level of SKILL (Ta-Daaa!) because you have to time and coordinate your control abilities very carefully, as opposed to simply slapping them on top of each other like we do know.  Your skill ceiling just got higher. 

Thoughts, comments?